Silicon dioxide (SiO2) was a reliable dielectric at the beginning of the semiconductor industry. As devices have continued to shrink and the technology has moved from “Full Si” transistor to “Metal Gate/High-k” in the case of transistors, the reliability of the SiO2-based gate dielectric is reaching its physical limits. One solution is to use other materials, such as hafnium-based or zirconium-based metal oxides for gate dielectrics. High-k materials (so-called because of their high dielectric constant) are becoming a material of choice since they can be made much thicker than SiO2 while achieving the same gate capacitance.
Singh et al. (US Pat. App. Pub. No. 2007/0259111A1) describes forming hafnium oxide films using chlorinated hafnium precursors such as HfCl2(tBuCp)2, HfCl2Cp2, HfCl2(EtCp)2, HfCl2(MeCp)2, HfCl3(Me5Cp), HfCl2(iPrCp)2 and HfCl3(iPrCp).
Itsuki et al. (JP200509766A) describes the use of HfCl3Cp for deposition of Hf-containing films by MOCVD; respectively Kim et al. (KR2007121281A) described the synthesis method or ZrCl3Cp as a precursor for deposition methods.
Other sources and methods of incorporating such materials are being sought for new generations of integrated circuit devices.